Lace bugs discolor azalea, hawthorn, and other leaves

Azalea lace bug stippling damage. Photo: SD Frank

Lace bugs have been out most of the summer but the damage is becoming apparent now as populations grow. Lace bugs damage plant cells and as the cells die necrotic spots and stippling appear. This can be exacerbated by plant stress and drought. Unfortunately, without scouting, most lace bugs go unnoticed until damage appears. This doesn’t have to be the case though. Lace bugs are very predictable and easy to find. They typically occur on the same plants year after year due to their lifecycle. Azalea lace bugs (Stephanitis pyrioides) overwinter as eggs inserted into leaves along the medial vein. Thus, if a plant had azalea lace bugs last year it will certainly have them this year. Likewise, hawthorn lace bugs (Corythucha cydoniae) overwinter as eggs in leaves or as adults in leaf litter or other sheltered location near the plant. Hawthorn lace bugs are also strong fliers that can easily travel to new host plants.

Hawthorn lace bugs on pyracantha. Photo: SD Frank

Hawthorn lace bugs feed on Rosaceous plants. I most frequently see hawthorn lace bug on cotoneaster, hawthorn, and serviceberry. I found a pyracantha plant on campus that was especially loaded down with hawthorn lace bugs. When I looked closer I found fire ants tending aphids on the tips of the branches. Often ants that are tending aphids will kill all other herbivores that would compete with the aphids and predators that would kill the aphids. In this case the ants didn’t seem to be tending the lace bugs but were also not destroying them. The lace bugs were definitely benefiting from ant protection though.

Sycamore lace bugs (Corythucha ciliata) are also very common. They feed on sycamore. They really do a number on sycamore leaves and later in the year heavily infested sycamores start looking pretty bad. Like other lace bugs, the sycamore lace bug causes stippling damage by piercing the underside of leaves with its stylet and sucking out the fluids. Large yellow and gray areas develop on the top of the leaves. In some cases, most leaves on a tree can be entirely covered in stippling damage.

There are at least a dozen of lace bug species and I cannot cover them all in this post I plan (and have written) other posts to discuss other species and to cover these species in depth. Lace bugs can be killed with horticultural oil or soap if you can get good coverage. You can also use systemic insecticides such as imidacloprid, Acelepryn, and Xxpire. http://www.ces.ncsu.edu/depts/ent/notes/Ornamentals_and_Turf/shrubs/ort039e/ort039e.htm